In many fields of military, national defense, aerospace, etc., detectors need to have characteristics such as high sensitivity, miniaturization, and strong anti-irradiation capability. Compared to an average radiant energy (˜30 eV) required by a conventional gas radiation detector to generate a detection signal by gas ionization, a semiconductor material requires an average radiant energy of <10 eV for generating a pair of electron-hole pairs, and thus at the same radiant energy, especially for a weak signal, a sensitivity of the semiconductor materials is higher than that of the gas. In the meantime, since the semiconductor material has a density greater than the gas, a very thin layer of the semiconductor material (a few microns) can effectively convert the absorbed radiant energy, which has a natural advantage in device miniaturization. Moreover, a mechanical strength of the semiconductor material itself can be well self-supporting, and it is convenient to integrate and construct a detector array, thereby realizing an acquisition of target position information. The research of semiconductor nuclear radiation detector has been going on for more than half a century. It has been widely used in many fields such as nuclear science, astronomy, cosmo physics, nuclear energy utilization, industrial automation, nuclear power plant, nuclear medicine imaging, anti-terrorism and environmental monitoring.
At present, due to the maturity of the device technology, the advantages of materials, and the well-developed microelectronic processing technology, the elemental semiconductor-based X-ray detector represented by Group IV silicon and germanium are developed at the earliest, and the first generation of semiconductor materials, represented by silicon and germanium, have developed a more mature fabrication technology for the detector. Compared with silicon, germanium has the advantage of its relatively large atomic number and low energy for electron-hole pair generation, which makes a germanium-based detector have higher efficiency and energy resolution.
However, both silicon and germanium are sensitive to ambient temperature and weak in radiation resistance due to their narrow band gap, so it is greatly restricted to equip them into a system working in space environment. On the other hand, for compound semiconductors, such as Group III-V compound GaAs, InGaAs and GaN, Group II-VI compound CdTe (energy resolution 0.3% @ 662 keV gamma ray, requires Peltire refrigeration) and CdZnTe, Group VII-μ dibasic halogen compounds HgI2, PbI2, TlBr and their ternary compound HgCdTe, etc., most of these materials have the disadvantages of low melting point, easy decomposition, and weak anti-irradiation capability, and stability and reliability of performance of the device constructed based on these materials is difficult to guarantee. These problems greatly limit the application of related detectors in harsh environments such as nuclear power plant and space.
In contrast, ZnO wide bandgap semiconductor materials with superior anti-irradiation capability, wider band gap, and higher breakdown electric field strength have attracted attention gradually. However, how to obtain high resistivity and thereby strongly suppress dark current noise in order to obtain high-resistivity single crystal ZnO with high signal-to-noise ratio has been an important obstacle hindering its application in the field of radiation detection.